I have a Samsung Galaxy Watch and it appears this is *still* a problem. Even worse, even if I explicitly ask for the weather in celsius, it still tells me in fahrenheit. Unfortunately for me, I bought my watch in America and after a lengthy chat with Samsung support, there's no option for changing the region of the watch. I'm going to try a local service center, but I'm not holding my breath...

My Samsung watch reports in Centigrade, as does bixby now so it has to be a software adjustment rather than a hardware one. I suspect your problem will be to find someone who knows how to make the adjustment. Good luck. If you keep asking Google it's highly likely someone has a solution.